Doesn't really help that 4 hour window that is the goal in the UK though.
We have that problem here, as well, to a certain degree. There are certain factors to keep in mind, though.
1) Our ERs operate on a triage system, where you're seen in order of priority. Everyone is assessed within a few minutes of arriving. So, if there are people coming in with life threatening conditions, they'll be seen immediately, people with the sniffles may have to wait.
2) For people with the sniffles, in addition to their primary care physicians (or instead of, in the case of people who don't have GPs), we also have after hours clinics they could go to that are more appropriate for treating minor things than the ER is.
3) I don't have a great deal of sympathy for people who go to the ER at 11 pm for a cold they've had for several days, and then find that they have to wait.
4) Much of the wait times are seasonal, having to do with levels of colds/flus in the community. Or, if there's a high level of traffic accidents on a given day/evening, they get behind as well.
All that said, my mom has to go to the ER when she has a chest cold, due to an underlying heart condition, because her GP's office and walk in clinics just don't have the testing equipment available to tell the difference between the two conditions. She is ALWAYS seen immediately.
5) Is the trade-off of having to wait a few hours for minor illnesses to be treated worth knowing that all people in this country are on a level playing field regarding the care that they receive, and that it's free, with no one being left out or financially devastated? Absolutely.